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 A215049 Number of primes of the form 1 + b^8 for 1 < b < 10^n. 13
 2, 2, 40, 335, 2498, 20886, 174368, 1507722, 13300713 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primes 1 + b^8 are a form of generalized Fermat primes. It is conjectured that a(n) is asymptotic to 0.261599*li(10^n). LINKS Yves Gallot, How many prime numbers appear in a sequence ? FORMULA a(n) = A214454(8*n) - 1. EXAMPLE a(1) = 2 because the only Fermat primes F_3(b) where b<10^1 are the primes: 257, 65537. MATHEMATICA Table[Length[Select[Range[2, 10^n-1]^8 + 1, PrimeQ]], {n, 5}] (* T. D. Noe, Aug 01 2012 *) PROG (PARI) a(n) = sum(b=1, 10^n/2-1, isprime((2*b)^8+1)) CROSSREFS Cf. A214454. Sequence in context: A222668 A210246 A116567 * A087541 A153434 A152016 Adjacent sequences:  A215046 A215047 A215048 * A215050 A215051 A215052 KEYWORD nonn AUTHOR Henryk Dabrowski, Aug 01 2012 STATUS approved

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Last modified July 25 03:53 EDT 2021. Contains 346283 sequences. (Running on oeis4.)